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HVAC
NATE Hydronics Gas Service Specialty
System Balancing
Knowledge Check
System Balancing
Knowledge Check
Knowledge Check
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A thermostat is calling for heat but the zone valve motor has opened and the boiler has not started. A technician measures voltage across the zone valve end switch terminals. What does 0 volts indicate?
A
The boiler's gas valve has failed
B
The circulator pump is locked out on thermal overload
C
The end switch has not closed because the valve is not fully open yet
D
The thermocouple is generating insufficient millivolts
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